Conducting System of Heart Different bioelectric signals n
Conducting System of Heart
Different bioelectric signals n The primary characteristics of typical bioelectric signals: Parameter Primary Signal characteristics Frequency range signal Amplitude Type of Electrode ECG 0. 05 to 120 Hz (100 Hz) 0. 1 - 5 m. V (1 m. V) Skin electrode EEG 0. 1 to 100 Hz (100 Hz) 2 - 200 u. V (50 u. V) Scalp electrode EMG 5 to 3000 Hz (100 Hz) 0. 1 - 5 m. V (50 u. V) Needle electrode ERG 0 -20 Hz 0. 5 uv-1 m. V Contact electrode EOG 0 -100 Hz 10 uv-3. 5 m. V Contact electrode
Electrode theory. Basic electrode, Electrodes for ECG n Electrode theory n Need, types of Bio-potential electrodes. n Basic electrode theory n Various Electrodes for ECG.
ELECTRODE - ELECTROLYTE & ELECTROLYTETISSUE INTERFACE
Electric equivalent circuits
Electrode theory- Basic electrode, n Need & Types of Bio-potential electrodes n n n Surface electrodes Deep seated electrode Factors to be consider while measurements: Ø Careful and suitable selection of electrodes for satisfactory record of bioelectric signal. Ø Comfortable for the patients to wear over long period Ø They should not produce any moving artefacts Ø Convenient in practical applications Ø Good contact with skin (for low contact impedance)
Cont. . n The characteristics of a metalic/nonmetalic surface electrodes depends uponn Condition at metal-electrolyte interface n Electrolyte –skin interface n Quality of electrolytes n Electrode properties Why electrode jelly is required while measurements of biopotential signals?
Cont. . n Electrode Potentials All electrode potentials are measured wrt a ref. Electrodes n Ref. Electrodes-Hydrogen electrode (H absorbed on platinum back -Calomel electrode Metal Ionic symbol Electrode potentials of few metal electrodes wrt Hydrogen Potential(Volt) n Aluminium Al+++ -1. 66 Iron Fe++ -0. 44 Lead Pb++ -0. 12 Hydrogen H+ -0. 0 Copper C++ +0. 34 Silver Ag+ +0. 80 Platinum Pt+ +1. 2 gold Au+ +1. 69
Cont. . q potential between Electrode s in electrolyte Electode Metal Electrolyte Potential difference between Electrode (m. V) Stainless steel Saline 10 silver Saline 9. 4 Silver-silver chloride Saline 2. 5 Silver-silver chloride (11 mm disc) ECG paste 0. 47 Silver-silver chloride (sponge) ECG paste 0. 2
L 6: Electrodes for ECG, EEG, EMG n Electrodes for ECG. n Electrodes for EEG, n Electrodes for EMG, n Biochemical Electrodes
Electrodes for ECG, EEG, EMG Electrodes are used to pickup the biopotentials from the surface of the body of from inside the cells. Basic electrodes are classified as: v v v Skin surface electrodes Needle electrodes Microelectrodes
Electrodes for ECG, EEG, EMG n Various Electrodes used for the measurement or recording of ECG signal. n v v v v Immersion electodes(not used now) Limb electrodes Suction cup electrodes Floating electrodes Spray –on electrodes Pregelled disposable electrode Pasteless (dry) electrodes Air –jet ECG electrodes
ECG plate electrode. The electrode is usually Fastened to the arm or leg with a perforated Rubber strap which keeps it in position during ECG recording Light weight floating Electrode with press Stud for long term monitoring ECG Electrodes
ECG Electrodes
Disposable pre-gelled ECG Electrode. A porous tape overlaying placed over the electrode resists perspiration and Ensures positive placement Under stress conditions Air –Jet ECG Electrodes
Suction cup electrode (Unipolar chest ECG Electrode. ) Floating type skin surface ECG Electrodes 18
Electrodes for ECG, EEG, EMG n Various Electrodes used for the measurement or recording of EEG signal. v v v Scalp surface electrodes (chlorided silver discs) Ear-clip electrodes (reference electrode) Small needle electrodes Silver ball or pellet electrodes(exposed cortex, high resistance) Pad electrode(silver ball is belled out at the end and padded with a sponge) Chlorided silver wire in plastic cup electrodes
EEG Electrode which can Be applied to the surface Of the skin by an adhesive tape. Ear-clip Electrodes & EEG scalp surface Electrodes EEG Electrodes
EEG Electrodes
Electrodes for ECG, EEG, EMG n Various Electrodes used for the measurement or recording of EMG signal. v Needle electrodes v v n Monopolar Bipolar Concentric core needle Multi-element needle electrodes Biochemical Electrodes n n n Reference electrode p. H electrodes Blood Gas electrode
EMG Electrodes
Micro Electrodes
Metal micro-electrodes
Biochemical Electrodes n n n Reference electrode p. H electrodes Blood Gas electrode v p. O 2 Electrode v p. CO 2 Electrode
L 7, L 8: Nernst eq. & Skin contact impedance n Nernst equation n Skin contact impedance measurement n Motion artifacts
Nernst Equation: VM Umale Dept. of Electronics and Telecommunication Engineering
SKIN CONTACT IMPEDANCE MEASUREMENT: Dept. of Electronics and Telecommunication Engineering
: Dept. of Electronics and Telecommunication Engineering
L 9: Physiological System of Heart v Physiology of Heart v Physiological System of Heart- Hydraulic system v Physiological System of Heart- electrical conduction
Conducting System of Heart
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